Not Applicable.
This invention relates generally to orthodontic devices and, in particular, to an improved jaw expander to widen a patient""s jaw.
Orthodontists treating children often need to gain space in a child""s mouth for unerupted mandibular incisors and to increase intercanine distance for narrow archforms, as well as to distilize mandibular first molars so that a total increase of archlength is available in the lower dental arch from first molar to first molar. Furthermore, the orthodontist may want to expand the palate correspondingly.
Mandibular and maxillary arch expanders are known in the art to expand and lengthen the mandibular and maxillary archlengths. The use of such arch expanders help avoid the need for tooth extraction of permanent teeth due to overcrowding. However, such mandibular arch expanders are rather bulky in design, impede tongue mobility, are uncomfortable to wear, and interfere with good oral hygiene. The devices must be substantial in design to resist torquing or leverage mechanics during chewing.
To facilitate corresponding enlargement of the maxillary and mandibular arches, telescoping mechanisms have been employed which encourage forward repositioning of the lower jaw as the patient closes into occlusion. Such devices are commonly referred to as Herbst appliances. Current Herbst appliances include a hollow tube and a rod which is telescopically received in the tube. The tube is connected to the maxillary arch expander and the rod is connected to the mandibular arch expander. Generally, the tube and rod are connected to a band or stainless steel crown by a pivoting connection. The pivot generally comprises a base casing which is soldered or welded to the band or crown and a screw that is inserted through an eye formed on the end of the hollow tube or rod. The screw threadedly engages the base casing and tightened, leaving enough clearance for the eye to pivot about the screw. Often the orthodontist uses an arch wire connected between the two ends of the arch expander. In the past, to accommodate the arch wire, the orthodontist or technician first must attach a rectangular wire tube to the band or crown and then attach the base case on top of the rectangular tube. This arrangement has a relatively high profile caused by the stacking of the rectangular tube and base casing along with the increased solder mass.
In this application, a new a telescoping assembly or advancing sheath and a expansion complex are provided for a maxillary or mandibular arch expander.
The telescoping assembly or advancing sheath includes a hollow posterior tube, a hollow anterior tube, and a rod extending through the two tubes. The anterior and posterior tubes are threadably connected so that the overall length of the advancing sheath can be selectively altered. An attachment is provided at a forward end of the posterior tube to pivotally mount the posterior tube to a tooth band. Another attachment is provided at the back end of the rod to pivotally connect the rod to a second tooth band. A spring is provided which extends between a forward end of the anterior tube and a forward end of the posterior tube. The spring urges the anterior tube rearwardly relative to the posterior tube to compensate for jaw pressure and to help prevent the jaw pressure from threading the anterior tube rearwardly.
In one embodiment, the posterior tube is externally threaded and the anterior tube is internally threaded. In this embodiment, the spring is journaled about the posterior tube. The posterior tube is provided with a stop forwardly of the end of the anterior tube, and the spring is positioned between the posterior tube stop and the forward end of the anterior tube. In a second embodiment, the posterior tube is internally threaded, and the anterior tube is externally threaded. In this embodiment, the spring is received within the hollow posterior tube and is journaled about the rod.
The expansion complex includes an outer housing and an advancing member which is telescopically received in the outer housing. The two portions of the expansion complex are received in opposed halves of a plate which fits against the mandibular or maxillary arch.
The outer housing includes side walls, a top, a bottom, a back, and an open front. A channel is formed in the housing top and extends rearwardly from the front of the housing. A threaded rod extends forwardly from the housing back wall beneath the channel to be accessible through the channel. At least one post (and preferably two posts) extend from the housing back wall parallel to the threaded rod.
The advancing member includes side walls, a bottom, a top, and a front wall. The advancing member is sized and shaped to e slidably received in the outer housing. A channel is formed in the advancing member top and extends rearwardly from the front wall. The advancing member channel is aligned with the outer housing channel.
To move the advancing member, an activation nut is threadably received on the threaded rod. The nut is accessible through the channels and movable along the threaded rod by rotation of the nut. An activation wing has a first plate slidably received on the threaded rod in front of the activation nut and a second plate slidably received on the post. The first and second plates are operatively connected to each other, and movement of the activation nut moves the first plate, and hence the second plate, relative to the housing and the advancing member. A spring is journaled about the post between the activation wing second plate and the advancing member front wall. When the spring is compressed, it effectively applies a pressure to the arch to force expansion of the arch.
Guides are provided to facilitate movement of the advancing member relative to the housing. The grooves of the outer housing and the advancing member are both defined by sloped walls, and the sloped walls of the advancing member channel are adjacent the sloped walls of the housing channel. Additionally, a groove is provided in the bottom surface of the advancing member and a corresponding rib is formed on the inner surface of the housing bottom. The rib and groove interaction, as well the interaction of the sloped walls, act as the guides for the movement of the advancing member.